A Double Torus

A double torus can be obtained by plotting the following function (thanks to H. Karcher):

     z = Sqrt[-x^4 + 2*x^6 - x^8 + 2*x^2*y^2 - 2*x^4*y^2 - y^4 + (2/10)^2]

Created by Wolfram Mathematica 6.0  (28 October 2007)